Astronomers using the Hubble Space Telescope discovered icy dwarf planet Pluto's fifth moon in 2012. In 2013, the International Astronomical Union (IAU) named the tiny satellite Styx. Styx was uncovered in a Hubble survey searching for potential hazards for the 2015 New Horizons spacecraft flyby of Pluto.

It is intriguing that such a small planet can have such a complex collection of satellites. The discovery provides additional clues for unraveling how the Pluto system formed and evolved. The favored theory is that all the moons are relics of a collision between Pluto and another large Kuiper belt object billions of years ago.

The moon is estimated to be 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system.

Discovery:
Styx was discovered on 26 June 2012 by a large team led by Mark Showalter using the Hubble Space Telescope.

How Styx Got Its Name:
Originally designated S/2012 (134340) 1 (and sometime referred to as P5), Styx is named for the mythological river that separates the world of the living from the realm of the dead. All of Pluto's moons are named for mythological figures associated with the underworld.